Electrical devices are commonly made up of individual components electrically connected together to form a single electrical circuit. An example of an electrical component well known in the art is a printed circuit board. Another example is a flexible printed circuit board, also known as a flexible circuit. Still another example is an integrated circuit, also referred to in the art as an IC chip. Advantageously, the IC chip may be electrically connected to a printed circuit board.
A typical IC chip is relatively small, such as a quarter of an inch in diameter, while the printed circuit board may be significantly larger. Previously, the chip has been included in a larger assembly, hereinafter referred to as a chip package, in order to provide sufficient surface area to electrically connect the chip to the printed circuit board. An example of a chip package includes a chip bonded to a lead frame. The lead frame is of sufficient size to make the electrical connection between a lead from the lead frame and another electrical device, such as a printed circuit board.
More recently, the chip has been included in a smaller assembly, approximately the same size as the chip, hereinafter referred to as a chip scale package. One example of a chip scale package includes a chip attached to a flexible circuit. A circuit trace within the flexible circuit performs a similar function as the leads of the lead frame. The traces in the flexible circuit are electrically connected to a first pad. The chip is bonded to the first pad such as with an adhesive. The chip is electrically connected to the first pad such as by wire bonding. A second pad is positioned on the other side of the flexible circuit opposite the first pad, and a plated through-hole electrically connects the pads. The second pad includes a plurality of solder balls. The solder balls serve as an electrical contact, to electrically connect the chip scale package to another electrical device, such as a printed circuit board.
A characteristic of the described chip scale package is that its reduced size makes it difficult to build, since it is difficult to route the circuit traces around the through-hole. Also, the narrow pitch between the solder balls makes it difficult to escape a wire from between the solder balls, in connecting the chip to another electrical device. Thus, there is a need in the art for a chip scale package that is more efficient to build and includes a more positive electrical contact for connecting the chip to another electrical device.